The present invention relates to a battery having a package structure for increasing the power storage capacity and output thereof, and more particularly to a battery, in which an upper bonding portion is folded toward the upper end of a battery case to increase the lengths of the battery case and an electrode assembly accommodated in the battery case in proportion to the reduced width of the bonding portion in a longitudinal direction to increase the power storage capacity and output of the battery at the same size of the battery package, and preferably, in which the inner corners corresponding to the upper bonding portion have large radiuses of curvature to provide excellent sealing capacity, and more preferably, in which upper and lower bodies of the battery case are separated from each other and receipt portions for receiving the electrode assembly are respectively formed in the upper and lower bodies to further improve the power storage capacity and output of the battery.
As shown in FIGS. 1A to 1E, a lithium ion polymer battery 10 comprises an electrode assembly 20, including an anode, a cathode, and a separator placed between the anode and the cathode, and a battery case 30 for receiving the electrode assembly 20 and a designated amount of electrolyte and hermetically sealing two electrode terminals 40 connected to corresponding taps of the anode and cathode of the electrode assembly 20 so that the two electrode terminals are exposed to the outside.
The battery case 30 includes a lower body 32 having a receipt portion 30a for containing an electrode assembly 20 and the designated amount of electrolyte, and an upper body 34, serving as a case cover, integrally connected to the lower end of the lower body 32. An extended portion having a designated width is formed along both sides and upper ends of the lower and upper bodies 32 and 34, thereby being used to bond the lower and upper bodies 32 and 34 to each other.
Hereinafter, with reference to FIGS. 1 to 5, an assembly process of the conventional lithium ion polymer battery 10 having the above-described package structure will be described in detail.
First, the electrode terminals 40 are connected to the corresponding taps of the anode and cathodes of the electrode assembly 20 by ultrasonic welding or spot welding. The electrode assembly 20 is placed in the receipt portion 30a of the lower body 32, and a designated amount of electrolyte is injected into the receipt portion 30a. The upper body 34 is covered on the lower body 32 such that the two electrode terminals 40 are exposed to the outside. The extended portions of the lower and upper bodies 32 and 34 contact each other and are pressingly heated using a thermal welding machine (not shown), thereby producing an upper bonding portion 30′ and side bonding portions 30″ of the battery case 30.
Thereafter, the side bonding portions 30″ of the lower and upper bodies 32 and 34 of the battery case 30 are folded at a right angle toward the neighboring sides of the battery case 30. A protection circuit 50 is placed on the upper bonding portion 30′ of the battery case 30 in the longitudinal direction of the battery case 30 so that the electrode terminals 40 are connected to corresponding portions of the protection circuit 50 (with reference to FIG. 5).
Since the length of the conventional battery having the above-described structure is limited and the upper bonding portion of the battery case of the conventional battery is extended along the longitudinal direction of the battery case, a component contained in the battery case, i.e., the electrode assembly, has a limited length, thereby decreasing the power storage capacity and the output of the battery.